This summer is not going to be easy !

On the topic of further on expanding the crop variety, Subbu has the following constraints.

a) "Sir, already the heat has started. This year we received heavy rain and all plants got used to ample of water. Now with the absence of that, past one month they are drooping. Let them settle down and get used scarce water. So I am going to 'train' them"

Satellite picture always shows clear sky these days.

b) Windpump is working absolutely fine. It gives plenty of water. However there is no wind for most of the day. (I referred to old anemometer recordings and found March-April are dull days).  But even though there is no wind,  even on windless days we get minimum one drum (1000 liters), thanks to the new foot valve that we changed few months back.  Windpump is working like well oiled machine. (indeed it is well greased)

Because more plants are there now compared to last year there is a demand for water.  But hope we can manage. Only I cannot expand my dream further of adding more varieties.

c) Presently the water that is pumped by windpump is just sufficient for all existing plants. "We feed water in round-robin fashion. We have the burden of sustaining all existing crops, having protected them with hardwork all these days", says Subbu.  He and Kandan had seen them growing from seeds. They know the pain of loosing crops in drought.

c) Casurina is still drinking water even though it has grown into adult tree and even started fruting.  If there is no water applied, the (Crown of) tree is showing its face down. Once a week is mandatory.

d) "Banana needs water too. There are around 200 trees. Let us not waste our money on purchasing Drip tubes. We just pour water from tank every alternate days through hose"

e) Jasmine to be watered. Though they consume less water. So also other plants like Sapota, lemon, guava and tamarind.  They are fed through drip irrigation.

f) Previously excess water was let into fish tank. Now the water is just sufficient.  With Sun soaring water level is coming down in the pond. This is exposing the fishes. A lot of birds (lot of them) are visiting our farm from all around.  Subbu says he cannot even identify the variety. So many of them.  Luck he.  I am missing the farm.  They are coming here for water and to eat fish.

Just an Illustration (Not to scale.)

I told Subbu to eat the fishes. It may be around 500 to 1000 of them. But he said let it be. want to see how big it grows. He wants me to come and see. But I told, just keep 40 and eat the balance. He wouldn't listen to. He has fallen in love with Fish.  He says it is a joy to see the fish playing. We can see them in clear waters.

g) Rice has come for harvesting. he wants to cut through rotovator (machine). I asked why not manually. He said it is better to cut through machine in one show. We have no manpower and it is cheap. Around Rs. 1000/- per hour is the rent. Don't know what is right thing to do. Anyway this time it was a demo for rice growing. Next time I will intervene.

h) For vegetable plots, Subbu advised let us not put Drip. Drip is useful only when space is more between the plants. In the case of Vegetables like brinjal, he is planning just 10 inches between.  So sprinkler is best.  He surprised me by saying that sprinkler is working even with the pressure of overhead tank. It is spraying few feet radius. That is enough. we can shift and manage it to cover all area.

So Sprinkler using gravitational force as planned. No motor. No electricity.  100% natural forces at work.

If this is not sustainable farming what is ?

Convinced at Last on Drip Irrigation

Subbu was "high" when I called him today.  He was so happy he did not want to talk to me further because his next best action was driving him mad.

He was thrilled that the drip irrigation pipes that he assembled worked very well.  No big deal for anyone who has heared the term drip irrigation in all magazines and advertisements. But is it another story when you actually "do it".

As mentioned earlier stories,  he had put the drip pipes around  the jasmine plants and other fence trees.  But due to lack of wind there was no water that was getting pumped by the windpump on to the overhead tank.  This tank would create required pressure to drive water to far off.

On laying the drip pipes,  we had taken a call that we will not take any professional help, but assemble ourselves.  We will also not go for any "filters and pumps" as in conventional system.  Ours will be simple low cost system where only pipes will be involved.  We would use gravity to drive water into pipes and leak out through rubber tubes where required.  Ofcourse we should maintain  the system "clean" to prevent clogging. That's all.

He said "Sir, actually this is the pipe I brought second time. The first time what I brought was not of good quality and it did not work. This is working well".  That is true, I had already advised him to buy sturdier 0/5 inch black rubber pipe instead of the widely commercialized flat drip tapes.  They will work only when you pump water with a force.  We donot have electricity or pump to drive the water.    Using a tank perched at 15 feet high, we  create enough gravitational force  to drive water to farthest corner of this 3 acre farm.

Anyway Kandan was very happy. He don't have to run around watering the stray plants manually.  In this hot summar it is very difficult to "carry" water on shoulders using plastic pots to water the stray plants.

Subbu is on his way to Tirunelveli to buy a bigger roll or pipes.

My Experiments on Water Tanking for Irrigation using gravity

Water storage and irrigation are an important aspect of Farming.  Storing Water when it is available and using it is needed with least energy is a must for dry lands.  Assuming wind pump will be installed by next month and the summer is fast approaching, I need to plan for water storage.  The pumped water and rain water need to be stored so that it can be used for all days with less energy. Since water tank would consume resources, there cannot be mistake in design and should be built with least cost.

My experimental setup on Cloth Hanger

The below doubts were always in my mind. Some of it had no answers in internet. Consulting an engineer will only add to more confusion.  So I ventured to find that out myself through home experiments. I used a plastic container as water tank, punctured holes, inserted think plastic tubes and started my experiment.  Used my cell phone camera and pictured the below using black chart paper for background on my balcony.  The below questions were to be answered.

1.  How to create water pressure using gravity ?
2.  Will the elevation of water tank above the ground level impact water pressure ?
3.  Can the water pressure from storage tank be used for sprinkler ?
4.  Will there be reduction in pressure due to coiling of tubes

Very tricky experiment

 Conclusions:

1.  Water pressure is the highest at the bottom of any water tank. This is due to weight of water pressing from above.  This pressure can be used to our advantage.  Once water is uplifted from ground level to an elevated storage tank, this pressure created by gravitational force or weight of water can be used to our advantage.  This also means that a taller and leaner water tank and a shallow wider tank may produce the same pressure at the bottom, given the volume of water being same. This is governed by formula P = gh where P is the water pressure, g is the acceleration due to gravity and h is the depth of the water at that point.  Here pressure P stands for pressure at any unit of water inside the tank and is same in all directions.

2. Water pressure increases slowly with elevation of water tank.  This experiment was very tricky. I failed in first attempt to understand the concept. I am still not convinced, but searched internet and repeated experiment with longer pipe.  then I have to believe it works.  The problem is everyone explains pressure increases as you move the water tank up further. But no one explains why?  Suppose if I move the water tank to sky high. Will I get infinite pressure at the bottom?

From Newton's Second law of Motion: 
Force = mass x accelaration
Force = volume x density x gravity
Force = height x area x density x gravity
Now force on per unit of area is pressue. Therefore  P=F/a
From the above equation P = height x  density x gravity

Here density of water and gravitational force remains the same. The only variable is height. Therefore as height increases so does pressure. Theoretically one must get additional 0.43 psi (pounds per square inch) of pressure for every foot moved up. 

When I used a long and short tube under the tank to find the pressure,  the pressure was almost same on both tubes. However when I repeated the experiment with further long tubes I could observe there was difference in fountain height of water - pressure.

So water tanks need to be built at an elevation to stay above the highest level on the farm at the least.  At the most it can be at any height.  There will be gain on pressure if you construct a water tank at 10 meter or 20 meter elevation from the ground.  The cost however would keep going up. There will also be challenges of constructing a large tank at that height and of pumping water to that height.

I am going to use windpump to pull the water up-to 10 to 15 feet above the ground level. And the tank has to be a large reservoir to store water for windless days.  Hence water tank if I construct should be at an elevation of 10 feet above the highest point to be irrigated on the farm and large enough. Increasing the height would be advantageous, but need to decide on construction material to be used etc... This point is still open.

An indigenous portable sprinkler

3. The pressure created by water tank is not enough to operate Sprinkler or a fountain. Smaller sprinkler can be operated, but not the ones that require high pressure. Therefore using gravity we can use drip irrigation effectively.  Small portable sprinklers can also be used for vegetable beds if enough pressure comes from a larger tank. I saw the one shown here in my neighboring garden.  Very beautiful idea and gives confidence how we can fabricate one ourselves without asking 'companies' to do 'survey and recommend' a suitable 'solution' to our 'problems'.   Earlier I used to think that I will keep a water tank at 30 feet and generate enough pressure to run a sprinkler. The learning is showing otherwise.

4.  Speed of water is reducing when it passes through coiled pipes due to friction.  It is therefore important to create straight lines to enable smooth flow of water for long distance. Otherwise for drip irrigation, nothing to panic. The pressure from water tank is sufficient to push the water to the corner of any pipe as the decrease of pressure due to viscosity matter only when water is 'flowing'. A moving water may experience pressure dip. But a water which fills a tube slowly will get compressed further by incoming water to be expelled through drip outlets.

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